Lectins, which are proteins capable of interacting with certain macromolecules and/or cell types via specific sugar moieties, are being used to investigate the interactions between saliva and/or bacteria in order to better elucidate the role these interactions play in plaque and caries development. Findings to date support the conclusion that 4 lectins, wheat germ agglutinin, concanavalin A, fucose binding protein and soybean agglutinin, can reversibly bind to and inactivate by complexation and/or precipitation the aggregating factor in saliva that is responsible for inducing the aggregation of Streptococcus mutans cells. These results provide evidence that the salivary aggregating factor contains N-acetyl-D-glucosamine (GlcNAc), D-mannose and/or D-glucose, L-fucose and N-acetylgalactosamine (GalNAc) and/or D-galactose (D-Gal). Lectins specific for D-Gal, D-GlcNAc, and D-GalNAc have been the most effective for the direct aggregation of oral bacteria.